2019-05-25T14:56:03Zhttps://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/1613532019-03-12T01:55:54Zcom_10261_88com_10261_8com_10261_82com_10261_34com_10261_5col_10261_341col_10261_335col_10261_287Modern sedimentary analogues and integrated monitoring to understand varve formation in the Mediterranean Lake Montcortès (Central Pyrenees, Spain)Trapote, M.C.Vegas-Villarrúbia, TeresaLópez, PilarPuche, EricGomà, JoanBuchaca, TeresaCañellas-Boltà, NúriaSafont, ElisabetCorella, Juan PabloRull, ValentíGeneralitat de CatalunyaMinisterio de Economía, Industria y Competitividad (España)Modern analoguesMediterranean regionBiogenic varvesSeasonal resolutionCalcite precipitationSediment trapsEste artículo contiene 13 páginas, 6 figuras, 1 tabla.Varved sediments provide unique opportunities to carry out high-resolution paleoclimatic and paleoenvironmental
reconstructions with accurate time control. To better interpret the sediment record it is necessary to
understand the physical, chemical and biological factors that influence varve formation and preservation. We
explored the link between the annual limnological cycle and current varve deposition in the oligotrophic hardwater
Lake Montcortès (Central Pyrenees). The varves of this lake consist of couplets of dark organic and light
calcareous laminae. A two-year limnological monitoring (10/2013–10/2015) combined with a sediment trap
study were conducted at monthly resolution. Limnological and sedimentological measurements were compared
with meteorological data. Although the lake was considered meromictic in the first limnological studies, we
documented total mixing of the water column both winters. In spite of this, long periods of stratification and
hypolimnetic anoxia create suitable conditions for varve formation and preservation. Sediment deposition followed
a clear seasonal pattern related to biological processes in the euphotic zone. During summer and fall,
calcite precipitation was favored by high calcite saturation indices and enhanced primary production that
promoted relatively high pH values as a result of CO2 uptaking. There was considerable variability in the amount
of calcite deposition between years, which was linked to seasonal temperature differences. In addition, calcite
crystal sizes and diatom fluxes showed seasonal patterns related to calcite saturation index and changes in water
stratification, which in turn were also related to temperature variability. Seasonal sedimentation patterns were
strongly linked to primary producers and especially sensitive to temperature shifts. It results in a clear seasonal
signal and varve formation. We compared our results with previous sedimentological interpretations of the
varved record of this lake. This study improves the interpretation of Lake Montcortès sediment record extending
back several millennia.This work was funded by the Ministry of Economy, Industry and
Competitiveness (project MONT-500; reference CGL2012-33665 with
an associated pre-doctoral research grant (FPI; BES-2013-065846); PI:
Teresa Vegas-Vilarrúbia) and the Catalan University and Research
Management Agency (AGAUR, project 2014 SGR 1207, PI: Meike
Köhler).Peer reviewed2018-02-27T07:50:29Z2018-02-27T07:50:29Z2018-02-02ArtículoPalaeogeography, Palaeoclimatology, Palaeoecology [in press] (2018)0031-0182http://hdl.handle.net/10261/16135310.1016/j.palaeo.2018.01.046http://dx.doi.org/10.13039/501100002809engMINECO/ICTI2013-2016/BES-2013-065846Postprinthttps://doi.org/10.1016/j.palaeo.2018.01.046SíembargoedAccesshttp://creativecommons.org/licenses/by-nc-nd/4.0/Elsevier